Relevant BUGIDs: 476963

Purpose of commit: new feature

Commit summary:
---------------
some applications are not prepared to get a SIGCHLD from a child
process they didn't think they launched, so we now suppress
this signal for the duration of use of the helper binary.
The 'noreap' module argument is provided to override this new
default.

1 files changed, 23 insertions, 3 deletions

diff --git a/modules/pam_pwdb/support.-c b/modules/pam_pwdb/support.-c
index e6d5829d..96f34609 100644
--- a/modules/pam_pwdb/support.-c
+++ b/modules/pam_pwdb/support.-c
@@ -79,8 +79,9 @@ typedef struct {
 #define UNIX_UNIX                19     /* wish to use /etc/passwd for pwd */
 #define UNIX_BIGCRYPT            20     /* use DEC-C2 crypt()^x function */
 #define UNIX_LIKE_AUTH           21     /* need to auth for setcred to work */
+#define UNIX_NOREAP              22     /* don't reap child process */
 /* -------------- */
-#define UNIX_CTRLS_              22     /* number of ctrl arguments defined */
+#define UNIX_CTRLS_              23     /* number of ctrl arguments defined */
 
 
 static const UNIX_Ctrls unix_args[UNIX_CTRLS_] = {
@@ -109,6 +110,7 @@ static const UNIX_Ctrls unix_args[UNIX_CTRLS_] = {
 /* UNIX_UNIX */		  { "unix",           _ALL_ON_^(050000),  01000000 },
 /* UNIX_BIGCRYPT */	  { "bigcrypt",       _ALL_ON_^(020000),  02000000 },
 /* UNIX_LIKE_AUTH */	  { "likeauth",       _ALL_ON_,           04000000 },
+/* UNIX_NOREAP */         {"noreap",          _ALL_ON_,          010000000 },
 };
 
 #define UNIX_DEFAULTS  (unix_args[UNIX__NONULL].flag)
@@ -342,13 +344,15 @@ static void _cleanup_failures(pam_handle_t *pamh, void *fl, int err)
  * verify the password of a user
  */
 
+#include <signal.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
 static int pwdb_run_helper_binary(pam_handle_t *pamh, const char *passwd,
-				  const char *user)
+				  unsigned int ctrl, const char *user)
 {
     int retval, child, fds[2];
+    void (*sighandler)(int) = NULL;
 
     D(("called."));
     /* create a pipe for the password */
@@ -357,6 +361,18 @@ static int pwdb_run_helper_binary(pam_handle_t *pamh, const char *passwd,
 	return PAM_AUTH_ERR;
     }
 
+    if (off(UNIX_NOREAP, ctrl)) {
+	/*
+	 * This code arranges that the demise of the child does not cause
+	 * the application to receive a signal it is not expecting - which
+	 * may kill the application or worse.
+	 *
+	 * The "noreap" module argument is provided so that the admin can
+	 * override this behavior.
+	 */
+	sighandler = signal(SIGCHLD, SIG_IGN);
+    }
+
     /* fork */
     child = fork();
     if (child == 0) {
@@ -397,6 +413,10 @@ static int pwdb_run_helper_binary(pam_handle_t *pamh, const char *passwd,
 	retval = PAM_AUTH_ERR;
     }
 
+    if (sighandler != NULL) {
+        (void) signal(SIGCHLD, sighandler);   /* restore old signal handler */
+    }
+
     D(("returning %d", retval));
     return retval;
 }
@@ -468,7 +488,7 @@ static int _unix_verify_password(pam_handle_t *pamh, const char *name,
 	if (geteuid()) {
 	    /* we are not root perhaps this is the reason? Run helper */
 	    D(("running helper binary"));
-	    retval = pwdb_run_helper_binary(pamh, p, name);
+	    retval = pwdb_run_helper_binary(pamh, p, ctrl, name);
 	} else {
 	    retval = PAM_AUTHINFO_UNAVAIL;
 	    _log_err(LOG_ALERT, "get passwd; %s", pwdb_strerror(retval));